And regarding ninja: I dread to add more dependencies (problems) to the annoying travis environment. Besides, make vs ninja can't make that big difference when building from scratch in a single-core one-by-one build surely?

It seems to be a false positive on thread-local memory, possibly caused by a buggy/old valgrind version. Since we already run many tests with valgrind enabled, I figured switching it off for the boringssl build is an okay work-around.